Soft Mineral Used in Plaster

This page is the CodyCross answer for the clue below from Medieval Times, Group 238, Puzzle 1 (Code of Justinian).

Question is: Soft Mineral Used in Plaster

and the answer is: GYPSUM

Word Meaning:

GYPSUM — A mineral consisting of hydrated calcium sulphate. When calcinated, it forms plaster of Paris.

Definitions from Wiktionary.